1. Field of the Invention
The present invention relates to devices used for rapid inflation and deployment of inflatable structures such as evacuation slides, rafts and the like, and more particularly it relates to aspirators utilized for this purpose.
2. Description of the Prior Art
Rapid inflation systems are currently used in various applications, but have achieved significant commercial recognition in the aviation industry in connection with the rapid inflation of evacuation slides and life rafts deployed during emergency situations. Typical rapid inflation systems incorporate an aspirator functioning in accordance with the Venturi principle. Specifically, such aspirators utilize pressurized primary gas to induce, or aspirate, a secondary gas or ambient air to combine with the pressurized gas to effect rapid inflation of the inflatable structure. The pressurized primary gas is rapidly introduced into the aspirator assembly through a nozzle arrangement. The rapid introduction of pressurized primary gas creates a partial vacuum within the aspirator assembly, thereby entraining the secondary gas or ambient air to enter the aspirator assembly. Once inside the aspirator assembly, the ambient air generates a combined air-gas flow mixture. This combined air-gas flow exits the aspirator through a discharge region of the aspirator capable of being disposed within an inflatable structure. Thus, the aspirator assembly uses a relatively small volume of pressurized primary gas to entrain a relatively large volume of a secondary gas or ambient air to inflate an inflatable structure. The efficiency of the aspirator assembly is often measured by its xe2x80x9cmass-flow ratioxe2x80x9d, or xe2x80x9caugmentation ratio,xe2x80x9d which is a ratio of the volume of primary gas used by the aspirator assembly to the volume of secondary gas or ambient air entrained by the aspirator assembly.
In the prior art, turbo or fan-type impeller driven aspirators used for inflating relatively large inflatable articles, such as airplane escape slides and rafts, are typically provided hard mounted to a fixed structure physically independent of the inflatable article. Generally, permanent attachment to the greater mass is required to compensate for external movement or gyration of the aspirator resulting from internal forces generated during operation of the aspirator. For example, external mounting is necessary to support the rotation of an unbalanced single impeller, such as a fan, and to withstand corresponding reactive inertial forces. For instance, aspirators for aircraft escape slides are generally provided within the body of the aircraft secured to a fuselage wall or other aircraft framework. It is necessary to bolt or otherwise permanently secure the aspirator to a frame or other external structure having mass substantially greater than the mass of the aspirator itself. The movement or gyration of an aspirator directly attached to an inflatable article introduces an often substantial risk of damage to the aspirator and/or inflatable article.
It is well recognized in the art that it should be advantageous to be able to attach an aspirator directly to an inflatable article. In the case of an aircraft, there are numerous internal systems that can negatively affect operation of an internally mounted aspirator and, thus, reliability of the evacuation procedure. Consequently, the ability to reposition an aspirator from the interior of an aircraft to the evacuation slide or life raft itself would make the entire evacuation system more independent and reliable. Furthermore, directly attaching the aspirator to the inflatable article would enable greater utilization of surrounding environmental atmospheric air, thereby enhancing inflation speed and efficiency.
Accordingly, there is an established need for an aspirator overcoming the aforementioned drawbacks and limitations of the prior art. In particular, it would be desirable to provide an aspirator assembly capable of being directly mounted to an inflatable structure, such as an escape slide or life raft, while maintaining stability of the aspirator with respect to the inflatable structure and, thereby, avoiding damage to the inflatable structure from external forces generated during operation of the aspirator. Furthermore, it would be desirable to provide such an aspirator having an improved mass-flow ratio, while maintaining a ace, simplified design lending itself to cost-effective manufacture.
The invention is directed to an aspirator assembly particularly adapted for the rapid inflation of relatively large inflatable structures such as emergency escape slides and life rafts found on aircraft.
One aspect of the present invention provides an aspirator assembly capable of providing faster and more efficient inflation of inflatable articles.
A further aspect of the present, invention provides an aspirator assembly having internal components designed and configured in a manner encouraging neutralization of generated internal forces during operation.
Still a further aspect of the present invention provides an aspirator assembly having a force balancing construction wherein gyrations and other external aspirator body forces are substantially neutralized during operation to enable direct attachment of the aspirator to an inflatable article without imparting undue loads thereto, thereby preventing ripping/tearing of the article material and entanglement between the aspirator and article material.
Yet a further aspect of the present invention provides an aspirator assembly having a relatively lightweight, simple, and low cost construction.
The invention provides an aspirator assembly adapted for direct attachment to inflatable articles, including: a generally cylindrical open-ended body having opposite upstream and downstream ends; a main conduit member disposed within and attached to the housing and disposed transverse to the longitudinal central axis thereof, the main conduit having an inlet for introducing a first pressurized gas therein and at least a pair of exit nozzles for directing a balanced flow of pressurized gas downstream therefrom; a central shaft extending downstream from the main conduit along the central axis of the aspirator body; and at least one pair of adjacent counter-rotating impeller members rotationally mounted on the central shaft, wherein the impellers include central vane portions and outer blade portions having mirror image surface geometries.
During operation of the aspirator, the first pressurized gas is directed through the exit nozzles to impinge upon the central internal vanes of a primary impeller in a radial symmetric fashion, causing substantially planar rotation of the primary impeller. This creates a pressure gradient for entraining a secondary gas or ambient air into the main body and directed downstream toward the secondary impeller. Internal flow swirl velocities generated by primary impeller rotation effect corresponding counter-rotation of the secondary impeller. The counter-rotating secondary impeller recovers the kinetic energy from the induced swirl velocities and counteracts the generated inertial forces to substantially neutralize internal forces within the aspirator body.